US3013956A - Methods of etching metals in the platinum group and producing printed circuits therefrom - Google Patents
Methods of etching metals in the platinum group and producing printed circuits therefrom Download PDFInfo
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- US3013956A US3013956A US651009A US65100957A US3013956A US 3013956 A US3013956 A US 3013956A US 651009 A US651009 A US 651009A US 65100957 A US65100957 A US 65100957A US 3013956 A US3013956 A US 3013956A
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- rhodium
- resist
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- electrolyte
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical group [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 title claims description 60
- 238000000034 method Methods 0.000 title claims description 45
- 238000005530 etching Methods 0.000 title claims description 30
- 229910052751 metal Inorganic materials 0.000 title description 37
- 239000002184 metal Substances 0.000 title description 37
- 150000002739 metals Chemical class 0.000 title description 15
- 239000003792 electrolyte Substances 0.000 claims description 74
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 38
- 239000002253 acid Substances 0.000 claims description 34
- 229910052742 iron Inorganic materials 0.000 claims description 18
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 claims description 16
- 229910052793 cadmium Inorganic materials 0.000 claims description 15
- LQBJWKCYZGMFEV-UHFFFAOYSA-N lead tin Chemical compound [Sn].[Pb] LQBJWKCYZGMFEV-UHFFFAOYSA-N 0.000 claims description 6
- 229910052703 rhodium Inorganic materials 0.000 description 120
- 239000010948 rhodium Substances 0.000 description 120
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 120
- 239000011248 coating agent Substances 0.000 description 59
- 238000000576 coating method Methods 0.000 description 59
- 229910000679 solder Inorganic materials 0.000 description 36
- 229910052697 platinum Inorganic materials 0.000 description 23
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 17
- 239000000463 material Substances 0.000 description 17
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 15
- 229910052718 tin Inorganic materials 0.000 description 15
- 239000011521 glass Substances 0.000 description 14
- 239000000203 mixture Substances 0.000 description 13
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 12
- 229960000443 hydrochloric acid Drugs 0.000 description 8
- 235000011167 hydrochloric acid Nutrition 0.000 description 8
- 239000012777 electrically insulating material Substances 0.000 description 7
- 229910052736 halogen Inorganic materials 0.000 description 7
- 238000004090 dissolution Methods 0.000 description 6
- 150000002367 halogens Chemical class 0.000 description 6
- 230000000873 masking effect Effects 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- RSWGJHLUYNHPMX-UHFFFAOYSA-N Abietic-Saeure Natural products C12CCC(C(C)C)=CC2=CCC2C1(C)CCCC2(C)C(O)=O RSWGJHLUYNHPMX-UHFFFAOYSA-N 0.000 description 4
- KHPCPRHQVVSZAH-HUOMCSJISA-N Rosin Natural products O(C/C=C/c1ccccc1)[C@H]1[C@H](O)[C@@H](O)[C@@H](O)[C@@H](CO)O1 KHPCPRHQVVSZAH-HUOMCSJISA-N 0.000 description 4
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 4
- 239000000919 ceramic Substances 0.000 description 4
- 238000007654 immersion Methods 0.000 description 4
- KHPCPRHQVVSZAH-UHFFFAOYSA-N trans-cinnamyl beta-D-glucopyranoside Natural products OC1C(O)C(O)C(CO)OC1OCC=CC1=CC=CC=C1 KHPCPRHQVVSZAH-UHFFFAOYSA-N 0.000 description 4
- BUGBHKTXTAQXES-UHFFFAOYSA-N Selenium Chemical compound [Se] BUGBHKTXTAQXES-UHFFFAOYSA-N 0.000 description 3
- 150000007513 acids Chemical class 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 239000004020 conductor Substances 0.000 description 3
- 239000007772 electrode material Substances 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- -1 platinum group metals Chemical class 0.000 description 3
- 229910052711 selenium Inorganic materials 0.000 description 3
- 239000011669 selenium Substances 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 2
- 229910000978 Pb alloy Inorganic materials 0.000 description 2
- 230000002939 deleterious effect Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 239000005357 flat glass Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- SKJCKYVIQGBWTN-UHFFFAOYSA-N (4-hydroxyphenyl) methanesulfonate Chemical compound CS(=O)(=O)OC1=CC=C(O)C=C1 SKJCKYVIQGBWTN-UHFFFAOYSA-N 0.000 description 1
- PFNQVRZLDWYSCW-UHFFFAOYSA-N (fluoren-9-ylideneamino) n-naphthalen-1-ylcarbamate Chemical compound C12=CC=CC=C2C2=CC=CC=C2C1=NOC(=O)NC1=CC=CC2=CC=CC=C12 PFNQVRZLDWYSCW-UHFFFAOYSA-N 0.000 description 1
- WUPHOULIZUERAE-UHFFFAOYSA-N 3-(oxolan-2-yl)propanoic acid Chemical compound OC(=O)CCC1CCCO1 WUPHOULIZUERAE-UHFFFAOYSA-N 0.000 description 1
- MARUHZGHZWCEQU-UHFFFAOYSA-N 5-phenyl-2h-tetrazole Chemical compound C1=CC=CC=C1C1=NNN=N1 MARUHZGHZWCEQU-UHFFFAOYSA-N 0.000 description 1
- 229910001369 Brass Inorganic materials 0.000 description 1
- 229910000925 Cd alloy Inorganic materials 0.000 description 1
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910001128 Sn alloy Inorganic materials 0.000 description 1
- 239000005083 Zinc sulfide Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- QZPSXPBJTPJTSZ-UHFFFAOYSA-N aqua regia Chemical compound Cl.O[N+]([O-])=O QZPSXPBJTPJTSZ-UHFFFAOYSA-N 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000010951 brass Substances 0.000 description 1
- 229910052980 cadmium sulfide Inorganic materials 0.000 description 1
- UHYPYGJEEGLRJD-UHFFFAOYSA-N cadmium(2+);selenium(2-) Chemical compound [Se-2].[Cd+2] UHYPYGJEEGLRJD-UHFFFAOYSA-N 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 210000003298 dental enamel Anatomy 0.000 description 1
- ZZUFCTLCJUWOSV-UHFFFAOYSA-N furosemide Chemical compound C1=C(Cl)C(S(=O)(=O)N)=CC(C(O)=O)=C1NCC1=CC=CO1 ZZUFCTLCJUWOSV-UHFFFAOYSA-N 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- QFWPJPIVLCBXFJ-UHFFFAOYSA-N glymidine Chemical compound N1=CC(OCCOC)=CN=C1NS(=O)(=O)C1=CC=CC=C1 QFWPJPIVLCBXFJ-UHFFFAOYSA-N 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 229910052981 lead sulfide Inorganic materials 0.000 description 1
- 229940056932 lead sulfide Drugs 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 229910052763 palladium Inorganic materials 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 229920002120 photoresistant polymer Polymers 0.000 description 1
- 238000000053 physical method Methods 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- GGYFMLJDMAMTAB-UHFFFAOYSA-N selanylidenelead Chemical compound [Pb]=[Se] GGYFMLJDMAMTAB-UHFFFAOYSA-N 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000005476 soldering Methods 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 229910052984 zinc sulfide Inorganic materials 0.000 description 1
- DRDVZXDWVBGGMH-UHFFFAOYSA-N zinc;sulfide Chemical compound [S-2].[Zn+2] DRDVZXDWVBGGMH-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/02—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding
- H05K3/06—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding the conductive material being removed chemically or electrolytically, e.g. by photo-etch process
- H05K3/07—Apparatus or processes for manufacturing printed circuits in which the conductive material is applied to the surface of the insulating support and is thereafter removed from such areas of the surface which are not intended for current conducting or shielding the conductive material being removed chemically or electrolytically, e.g. by photo-etch process being removed electrolytically
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
- C23F1/10—Etching compositions
- C23F1/14—Aqueous compositions
- C23F1/16—Acidic compositions
- C23F1/30—Acidic compositions for etching other metallic material
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F3/00—Electrolytic etching or polishing
- C25F3/02—Etching
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14665—Imagers using a photoconductor layer
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
- Y10T29/49124—On flat or curved insulated base, e.g., printed circuit, etc.
- Y10T29/49155—Manufacturing circuit on or in base
- Y10T29/49156—Manufacturing circuit on or in base with selective destruction of conductive paths
Definitions
- the confronting electrodes of a photocell constructed in this manner be spaced by a small distance.
- the mass of photoconductor material extending between the electrodes is also small.
- lt is one of the objects of the present invention to provide a method of dissolving metals in the platinum group with a solvent which will not substantially attack conventional resist materials.
- l-t is a further object of the present invention to provide a method for etching such metals. provide an etching process for fabricating printed circuits with platinum group conductors.
- a body of a platinum group metal may be dissolved by disposing the body in a liydrohalic acid electrolyte and adjusting the potential of the body to be negative relative to the electrolyte.
- the inventors have also found that the proper potential relation between the electrolyte and the metal body may be achieved by placing a second metal mass in contact with the body which has a contact potential relative to the body making the body negative with respect to the second mass by the desired magnitude.
- rhodium and platinum bodies may be dissolved in an electrolyte, and hence etched, by disposing a mass of metal with a positive contact potential relative to the body of the order of that of lead on the surface of the body before placing it in contact with the electrolyte which includes a halogen acid.
- a rhodium or platinum body may be etched by placing a layer of resist on the body in the pattern desired to be sched, placing a mass of metal with a contact potentialr relative to the body of the order of that of lead on the body, and bringing the body and mass into lt has been found that the performance of photocells constructed in this manner has been adversely affected by diffusion of the electrode material into the photoconductor material.
- lnconel is employed for the electrodes, and this material diffuses into the photoconductor materials to produce a deleterious effect upon the photocell operation.
- Diffusion of the electrode material into the photoconductor material of the photocell and the deleterious eects thereof can be substantially eliminated by employing certain metals of the platinum group (the lower two rows of group Vlll oi the periodic table) as the electrode material.
- Rhodium and platinum for example, will not diiiuse to any substantial degree into the photoconductor materials employed in photocells.
- most ot the platinum group metals could not be etched, since the acids which will attack them also destroy the resists known to the art.
- the conventional method of removing rhodium, for example, from a glass mirror is to cmploy concentrated boiling sulfuric acid which is unsuitable in an etching process.
- Electrical printed circuits may thus be fabricated by coating an electrically insulating substrate or base with rhodium, or platinum, placing a resist on the rhodium or platinum in the pattern of the electrical conductors, bringing the exposed portion of rhodium or platinum into contact with an electrolyte including a hydrohalic acid and causing the rhodium or platinum body to assume a negative potential relative to the electrolyte.
- FIGURE l is an elevational view of a photocell assembly constructed according to the teachings of they present invention.
- Pi-URE 2 is a sectional view taken along the line 22 of FIGURE l;
- FIGURE 3 is an elevational view of the photocell assembly shown in FIGURES l and 2 during the process of manufacture.
- FIGURE 4 is a schematic view of a device for practicing the invention.
- the photocell assembly has a iirst group 10 of spaced parallel bar-shaped electrodes disposed upon a substrate or base 12pt" electric-ally insulating material in the form of a plate.
- a second group i4 of parallelY elongated spaced bar-shaped electrodes confronts the electrodes of the iirst group 1l), one of the electrodes of the second group la being aligned with each of the electrodes of the rst group 10.
- a ribbon lo of photoconductive material of the semiconductor class is also disposed upon the base plate l2 and contacts each of the electrodes of both groups 10 and 14.
- the photocell lassembly is intended for use in an analogue to digital optical encoder in which the regions between electrodes of each group are masked oil from illumination, although it is to be understood that the photocell assembly has applications in addition to that of an optical encoder.
- the group lll of electrodes is fabricated as an integral unit due to a bar-shaped portion 18 which exelectrodes of the group 14, thus forming a common connection for the electrodes in group 10.
- the base plate 1 2 must be constructed of electrically insulating material and must not be soluble in the electrolyte. Glass has been found to be a preferred material for the base plate 12., although ceramics and plastics may also be employed.
- the first step in the fabrication of the photocell assembly is to place a coating of a metal of the platinum group, such as rhodium, designated 2S in FIGURE 3, on one surface of the base plate 12. Since rhodium coating of glass is conventional in the manufacture of mirrors, this step will not be further described.
- a suitable resist 22 in layer form having the pattern of the two groups 1f) and 14 of electrodes is disposed upon the coating 2f). This may be accomplished by painting a resist 22 onto the coating 20 through a stencil; suitable resists for this process being thermoplastic enamels or wax and rosin mixtures. Photographic resists may also be employed. The photographic method of placing the pattem of resist upon the coating is more accurate than the stencil method, and the inventors have found that commercially available photographic resists are particularly satisfactory.
- FIGURE 3 illustrates in solid lines the lump 24 spaced from the pattern of resist 22, and this is the situation when the resist 22 is placed upon the coating 20 prior to the lump.
- a mass of masking material designated 26 in FIGURE 3
- Wax has been found to be a suitable masking compound for the mass 26.
- the mass ⁇ of masking compound may then be physically scraped from the coating 2f) and the assembly re-immersed in the bath of electrolyte to remove ⁇ the strip that has maintained contact with the lump 24. This step is generally unnecessary, since the presence of the lump 24 in electrical contact with one group of electrodes generally facilitates electrical connections.
- the mass of masking material 26 is not necessary. Continuity between the lump and coating 2f) is achieved by the resist itself.
- the electrolyte employed must not appreciably attack the resist. Further, the inventors have found that for the dissolution of platinum group metals, the electrolyte must contain a hydrohalic acid, that is, an aqueous 4. solution of HF, HCI, HB1' and Hl. Dilute hydrochloric acid has been found to be a particularly suitable electrolyte.
- solder a lead-tin lump, commonly known as solder
- Solder with equal parts of lead and tin have been found to be particularly advantageous, although lead alone, iron, and cadmium may also be employed. Solder is considered preferable due to the ease with which it can be attached to the coating, ⁇ and to its resistance to attack by the electrolyte. Platinum will also dissolve in halogen acid electrolytes with a lump of lead, lead-tin, iron, or cadmium in contact with the platinum body.
- the resist defining the electrodes is removed. If commercially available photographic resists are employed, this may be accomplished by immersion in methyl ethyl ketone. The resist may also be removed by physical methods, such as scraping.
- the material employed for the photoconductive ribbon may be any photosensitive material. It has been found that particularly satisfactory photosensitive materials are those of the semiconductor class. Cadmium selenide, cadmium sulfide, lead sulfide, lead selenide, zinc selenide, zinc sulfide, zinc telluride, cadmium telluride, germanium, silicon and lead tellnride have all been found to be suitable.
- Solder in the form generally employed and referred to in this specification, is a mixture of lead and tin. Solder, like other lead and tin alloys, contains a euteetic of lead and tin depending upon the relative proportionsy of the lead and tin in the alloy.
- Example I The base 12 is a sheet of plate glass, and it is provided with a rhodium coating 20.
- the rhodium coating 20 is.
- solder 24 is placed upon the rhodium coating 20 spaced from the resist pattern 22.
- a lump 26 of wax is then placed upon the rhodium coating 20 between the lump of solder 24 and the resistant pattern 22, the wax extending into contact with both the solder and the resist pattern.
- the solder employed is 50-50 solder, i.e., equal parts of lead and tin.
- a bath containing a normal solution of hydrochloric acid at room temperature is employed to dissolve the rhodium coating 20, and does not appreciably attack the glass base plate 12 or the resist pattern 22.
- the resist 22 is Ithen removed by immersion in a bath of methyl ethyl ketone, and the ribbon 16 is formed by evaporating a layer of cadmium and selenium onto the base plate 12 and the two groups 10 and 14 of rhodium electrodes formed by the etching process, and heating for a period of one hour at 400 C.
- Example Il A coating of rhodium is placed on a sheet of ceramic.
- a mass of iron is disposed in contact with the rhodium coating.
- the resist consisting of 50% rosin and 50% wax is applied to the rhodium coating with a stencil and brush in the desired pattern.
- the resist is positioned on the rhodium coating to partially cover the edge of the iron mass.
- the ceramic, rhodium coating, resist and iron mass are then immersed in a bath of concentrated hydrouoric acid at room temperature.
- the ceramic, rhodium coating, resist and iron mass are then immersed for the period suliicient to dissolve the unprotected portion of the rhodium coating, approximately five to ten minutes.
- a suitable solvent ,5 is then employed to remove the wax and rosin composition from the confronting ends of electrodes of both groups.
- a ribbon is then 'formed by evaporating a layer of lead and selenium on the plate andelectrodes between and in contact with the confronting ends of the electrodes of the two groups.
- the base, electrodes and ribbon are then baked at a temperature of 400 C. for a period of one hour.
- Example III A platinum coating may be etched and used to form the electrodes of a photocell by substituting platinum for rhodium in either of the foregoing examples.
- cadmium, or alloys of lead, cadmium and iron may be substituted for the solder or iron. Best results, however, have been achieved by employing solder consisting of 50% lead and 50% tin. Further, it is not necessary that the lump be bonded to the rhodium or platinum surface, as is the case with soldering.
- the mass of material may be maintained in contact with the rhodium coated surface in any suitable manner. For example, a clip may be coated with solder and clipped on the base plate either before or during immersion so that it contacts the rhodium surface.
- the electrolytes may be replaced in Example I, Example 'Il and Example llll by mixtures of acids as long as one of the acids in the mixture is a halogen acid.
- a solution of hydrochloric andi sulfuric acid may be employed, or a solution consisting of 50% aqua regia and 50% HF and HC1.
- other halogen acids may be substituted for those disclosed in the above examples, for example iodic acid.
- FIGURE 4 illustrates the method of etching platinum ⁇ group metals in a halogen acid electrolyte with a potential source, ⁇ according to the teachings of the present invention.
- the electric potential source designated ⁇ 30, is connected between an electrically conducting electrode 32 and the coating of metal of the platinum group, the negative terminal of the source 30 being connected to the coating 20.
- Both the electrode 32 and the work piece including the coating Ztl are immersed in a body 34 of electrolyte including a halogen acid which is illustrated disposed within a vessel 36.
- the coating 20 must be maintained at a negative potential relative to the electrolyte.
- this potential supplied by the source must be between 0.75 volt and 1.00 volt for optimum results.
- the base 12 is a sheet of plate glass, and it is provided with a rhodium coating 20.
- the rhodium coating 20 is thenV provided with a layer of Kodak Photo Resist, andthe pattern of the two groups 10 and 14 of electrodes is then focused upon a photographic resist to expose it.
- the photographic resist is then developed in a developer for the photographic resist.
- a brass electrode is disposed in a bath of 1.0 normal solution of hydrochloric acid at room temperature, and connected to the positive terminal of a potential source.
- the negative terminal of the potential source is connected to the coating of rhodium by acopper wire, and the coating is immersed in the hydrochloricacid.
- the potential source is adjusted to make the coating 0.82 volt negative relative to the electrolyte, and the dissolution of the rhodium is permitted to complete.
- the resist 22, is then removed by immersion in a bath of methyl ethyl ketone, and the ribbon ld is formed by evaporating a layer of cadmium and selenium onto the base plate l2 and the two groups l0 and 14 of rhodium electrodes formed by the etching process, and heating for a period of one hour at 400 C.
- the method of etching a pattern in a body of metal in the platinum group comprising the steps of contacting the body with a mass of metal from the group consisting of lead, lead-tin, iron and cadmium, placing a layer of resist in the desired pattern on the body, and
- the method of etching an electrical circuit in a rhodium layer comprising the steps of coating a surface of a base constructed of electrically insulating material with a layer of rhodium, placing a mass of metal of the group consisting of lead, lead-tin, iron and cadmium on a portion of the surface of the rhodium layer, placing a layer of resist on the rhodium layer in the desired pattern, and placing the layer of resist, rhodium layer, and at least a portion of the metal mass in contact with an electrolyte consisting essentially of a hydrohalic acid,
- the method of etching an electrical circuit in la layer of rhodium comprising the steps of coating a surface of a glass plate with a layer of rhodium, placing a mass of solder comsisting essentially of a mixture of lead and tin on a portion of the surface ofthe rhodium layer, placing a layer of photographic resist on the rhodium layer, optically exposing a pattern of the desired electrical circuit on the photographic resist, developing the resist, and immersing the glass plate, rhodium layer, at least a portion of the mass of solder, and developed resist in an electrolyte consisting of hydrochloric acid, the contact potential of the mass and rhodium layer making the layer electrically negative with respect to th electrolyte.
- a method of etching a pattern in a rhodium body comprising the steps of placing a mass of solder consisting essentially of a mixture of lead and tin on a portion of the surface of the rhodium. body, placing a layer of photographic resist on the rhodium body, exposing the desired pattern on the photographic resist, developing the photographic resist, and immersing the body, mass of solder, and developed resist in an electrolyte consisting essentially of hydrohalic acid, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte.
- the method of etching an electrical' circuit vin rhodium comprising the steps of placing a mass of 'solder consisting essentially of a mixture -of lead and tin on a portion of the surface of the rhodium body, placing a layer of photographic resist on the rhodium body, exposing the desired pattern on the photographic resist, developing the photographic resist, and immersing theV body,
- the method of etching an electrical circuit in a layer of rhodium comprising the steps of coating a surface ofra glass plate with a layer of rhodium, placing a mass of solder consisting essentially of a mixture of lead and tin in equal parts on a portion of the surface of the rhodium layer, placing a layer of photographic resist on the rhodium layer, optically exposing a pattern of the desired electrical circuit on the photographic resist, developing the resist, immersing the glass plate, rhodium layer, at least a portion of the mass of solder, and developed resist in an electrolyte consisting of hydrochloric acid, the contact potential of the mass of solder and rhodium layer making the rhodium layer electrically negative with respect to the electrolyte, and then immersing the glass plate, resist and remaining rhodium layer in methyl ethyl ketone to remove the remaining resist.
- the method of etching a pattern in a rhodium body comprising the steps of placing a mass of solder consisting essentially of a mixture of lead and tin on a portion of the surface of the rhodium body, placing a layer of resist in the desired pattern on the rhodium body, placing the resist, rhodium body, and at least a portion of the mass of solder in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte, and removing the remaining resist.
- the method of etching an electrical circuit in a layer of rhodium comprising the steps of coating a surface of a glass plate with a la er of rhodium, placing a mass of solder consisting of a mixture of lead and tin in equal parts on a portion of the surface of the rhodium layer, placing a layer of photographic resist on the rhodium layer, optically exposing a pattern of the desired electrical circuit on another region of the photographic resist, developing the resist, placing a mass of wax between the mass of solder and the pattern of resist, and immersing the glass plate, rhodium layer, at least a portion of the mass of solder, and developed resist in an electrolyte consisting of hydrochloric acid, the contact potential of the mass of solder and rhodium layer making the rhodium layer electrically negative with respect to the electrolyte.
- the method of etching an electrical circuit in a layer of rhodium comprising the steps of coating a surface of a base constructed of electrically insulating material with a layer of rhodium, placing a mass of solder consisting essentially of a mixture of lead and tin on a portion of the surface of the rhodium layer, placing a layer of resist on another portion of the rhodium layer in the desired pattern, placing a mass of masking material between the solder and pattern of resist, and placing the resist, rhodium layer, and at least a portion oi the mass of solder in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass and rhodium layer making the layer electrically negative with respect to the electrolyte.
- the method of etching an electrical circuit in a layer of rhodium comprising the steps of coating one surface of a glass plate with a layer of rhodium, placing a layer of resist of wax and rosin in a desired pattern on the rhodium layer, placing a mass of solder consisting essentially of a mixture of lead and tin on the rhodium layer spaced from the resist, placing a mass of Wax on the rhodium layer extending between the mass of solder and the resist, immersing the glass plate, rhodium layer, and resist layer in an electrolyte consisting of hydrochloric acid to dissolve the rhodium layer adjacent to the layer of resist, mass of wax, and lump of solder, the contact potential of the mass of solder and layer of rhodium making the layer of rhodium electrically negative with respect to the electrolyte, and removing the exposed portion of the resist layer to expose the confronting rhodium electrodes.
- the method of etching an electrical circuit in a layer of rhodium comprising the steps of coating a surface of a base constructed of an electrically insulating material with a layer of rhodium, placing a mass consisting essentially of iron on a portion of the surface of the rhodium layer, placing a layer of resist von rhodium layer in the desited pattern, and placing the resist, rhodium layer, and at least a portion of the iron mass in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass of iron and rhodium layer making the layer electrically negative with respect to the electrolyte.
- the method of etching an electrical circuit in a layer of rhodium comprising the steps of coating a surface of a base constructed of an electrically insulating material with a layer of rhodium, placing a mass consisting essentially of cadmium on a portion of the surface of the rhodium layer, placing a layer of resist on the rhodium layer in the desired pattern and placing the resist, rhodium layer, and at least a portion of the cadmium mass in contact with an electrolyte consisting essentially of a hydro halic acid, the contact potential of the mass of cadmium and rhodium layer making the layer electrically negative with respect to the electrolyte.
- the method of etching an electrical circuit in a layer of rhodium comprising the steps of coating a surface of a base constructed of an electrically insulating material with a layer of rhodium, placing a mass consisting essentially of lead on a portion of the surface of the rhodium layer, placing a layer of resist on the rhodium layer in the desired pattern, and placing the resist, rhodium layer, and at least a portion of the lead mass in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass of lead and layer of rhodium making the layer electrically negative with respect to the electrolyte.
- the method of etching a pattern in rhodium comprising the steps of placing a mass consisting essentially of iron on a portion of the surface of the rhodium body, placing a layer of resist in the desired pattern on the rhodium body, and placing the resist, rhodium body and at least a portion of the mass of iron in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte.
- the method of etching a pattern in rhodium comprising the steps of placing a mass consisting essentially of cadmium on a portion ofthe surface of the rhodium body, placing a layer of resist in the desired pattern on the rhodium body, and placing the resist, rhodium body and at least a portion of the mass of cadmium in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte.
- the method of etching a pattern in rhodium comprising the steps of placing a mass consisting essentially of lead on a portion of the surface of the rhodium body, placing a layer of resist in the desired pattern on the rhodium body, and placing the resist, rhodium body and at least a portion of the mass of lead in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass and the body making the body electrically negative with respect to the electrolyte.
- the method of dissolving a metal body of the platinum group comprising the steps of placing the metal body of the platinum group in contact with an electrolyte consisting essentially of a hydrohalic acid, and contacting the body with a mass of metals of the group consisting of lead, lead-tin, iron and cadmium, said mass being in contact with the electrolyte, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte.
- the method of dissolving a body of platinum comprising the steps of placing the platinum body in contact with an electrolyte consisting essentially of a hydrohalic acid, ⁇ and contacting the body and electrolyte with a mass consisting essentially of lead, the contact potential of the metal mass and body making the body electrically negative with respect to the electrolyte.
- the method of dissolving a body of platinum comprising the steps of placing the platinum body in contact with an electrolyte consisting essentially of a hydrohalic acid, and contacting the body and electrolytewith a mass consisting essentially of cadmium, the contact potential of the mass and body making the body electrically negative with respect tothe electrolyte.
- the method of dissolving a body of platinum cornprising the steps of placing the platinum body in contact with an electrolyte consisting essentially of a hydrohalic acid, and contacting the body and electrolyterwith a mass 10 consisting essentially of solder with approximately equal parts of lead and tin, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte.
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Description
Dec, 19, 1961 F. B. HUGLE E'r AL 3,013,956
METHODS 0R ETcHING METALS IN THE PLATINUM GROUP AND PRoDUcING PRINTED CIRCUITS TREREERoM Filed April 5, 1957 1 l JG I if; gij; gli; iii; 1:1; i: 3;: iii: ;:3 :i: it; ii; i-: ijf; j.; LI L I L 7L L L{ FE E .Saure/e @TIME-mi a1- i 22 MMMMMMMMMMMIMMM a3;
FE E 20/ /UUQHUUH IN V EN TORS frances J3. Hayle Ul ZZL'aJzz HIL/g@ 3,lll3,56 METHDDS @F ETCHING METALS HN THE PLATE- NUM GRUUP AND PRODUCENG PRlNTED CIR- CUlTS THEREFROM Frances B Hugle and William l5. Hugle, Union Township, Clermont County, Ghia, assignors to The Baldwin Piano Company, Cincinnati, Ohio, a corporation of @hic Filed Apr. 5, 1957, Ser. No. 65ml@ 2l Elaims. (Cl. 20d-43) The present invention relates generally to methods of etching metals in the platinum group and more particularly to methods of manufacturing printed circuits with these metals.
Recently, printed circuit techniques have been applied to the fabrication of photocells. ln accordance with these techniques, an electrically conducting coating is disposed upon an electrically insulating substrate or base, and a resist is disposed upon the coating of electrically conducting material in the desired pattern to form two confronting spaced electrodes. The entire assembly is then immersed in a bath of solvent which removes the portion of the electrically conducting coating which iS not protected by the resist. The resist is then removed, leaving two confronting spaced electrically conducting electrodes on an electrically insulating base. A mass of photoconductor material, generally of the semicondoctor class, is then disposed on the base between the electrodes and in Contact with the electrodes, this step generally requiring the application of heat. The patent application of the present inventors entitled oemiConductive Films and Methods of Producing Them, Serial No. 574,804, iiled March 29, '1956, illustrates photocells constructed in this manner. Y
lt is often desirable that the confronting electrodes of a photocell constructed in this manner be spaced by a small distance. As a result, the mass of photoconductor material extending between the electrodes is also small.
Patented Dec. 19,1961
lt is one of the obiects of the present invention to provide a method of dissolving metals in the platinum group with a solvent which will not substantially attack conventional resist materials. l-t is a further object of the present invention to provide a method for etching such metals. provide an etching process for fabricating printed circuits with platinum group conductors.
The inventors have found that a body of a platinum group metal may be dissolved by disposing the body in a liydrohalic acid electrolyte and adjusting the potential of the body to be negative relative to the electrolyte. The inventors have also found that the proper potential relation between the electrolyte and the metal body may be achieved by placing a second metal mass in contact with the body which has a contact potential relative to the body making the body negative with respect to the second mass by the desired magnitude. More specically, rhodium and platinum bodies may be dissolved in an electrolyte, and hence etched, by disposing a mass of metal with a positive contact potential relative to the body of the order of that of lead on the surface of the body before placing it in contact with the electrolyte which includes a halogen acid. As a result of this discovery, a rhodium or platinum body may be etched by placing a layer of resist on the body in the pattern desired to be sched, placing a mass of metal with a contact potentialr relative to the body of the order of that of lead on the body, and bringing the body and mass into lt has been found that the performance of photocells constructed in this manner has been adversely affected by diffusion of the electrode material into the photoconductor material. Generally, lnconel is employed for the electrodes, and this material diffuses into the photoconductor materials to produce a deleterious effect upon the photocell operation. Diffusion of the electrode material into the photoconductor material of the photocell and the deleterious eects thereof can be substantially eliminated by employing certain metals of the platinum group (the lower two rows of group Vlll oi the periodic table) as the electrode material. Rhodium and platinum, for example, will not diiiuse to any substantial degree into the photoconductor materials employed in photocells. However, prior to the present invention, most ot the platinum group metals could not be etched, since the acids which will attack them also destroy the resists known to the art. The conventional method of removing rhodium, for example, from a glass mirror is to cmploy concentrated boiling sulfuric acid which is unsuitable in an etching process.
One well known method of catalyzing the dissolution of metals is to place the metal to be dissolved in Contact with a metal lower in 4the elec'tromotive series, and then place the two metals in au acid electrolyte. Under these conditions, the metal which is lower in theelectrornotive series catalyzes the dissolution of the other metal. The three lowest metals of the electromotive series listed in the Handbook of Chemistry and Physics, Chemical Rubber Publishing Co., 1953, are palladium, platinum and gold, in declining order. Rhodium catalyzes the dissolution of all three of these metals in the presence of an electrolyte, thus acting as if rhodium were lower in the electromotive series than the other of these metals.
Contact with an electrolyte containing a hydrohalic' acid which wili not appreciably attack the resist. Electrical printed circuits may thus be fabricated by coating an electrically insulating substrate or base with rhodium, or platinum, placing a resist on the rhodium or platinum in the pattern of the electrical conductors, bringing the exposed portion of rhodium or platinum into contact with an electrolyte including a hydrohalic acid and causing the rhodium or platinum body to assume a negative potential relative to the electrolyte. The invention will be more clearly understood from a further reading of this disclosure, particularly when viewed'in the light of the drawings, in which:
FIGURE l is an elevational view of a photocell assembly constructed according to the teachings of they present invention;
Pi-URE 2 is a sectional view taken along the line 22 of FIGURE l;
FIGURE 3 is an elevational view of the photocell assembly shown in FIGURES l and 2 during the process of manufacture; and
FIGURE 4 is a schematic view of a device for practicing the invention.
In lits completed form, the photocell assembly has a iirst group 10 of spaced parallel bar-shaped electrodes disposed upon a substrate or base 12pt" electric-ally insulating material in the form of a plate. A second group i4 of parallelY elongated spaced bar-shaped electrodes confronts the electrodes of the iirst group 1l), one of the electrodes of the second group la being aligned with each of the electrodes of the rst group 10. A ribbon lo of photoconductive material of the semiconductor class is also disposed upon the base plate l2 and contacts each of the electrodes of both groups 10 and 14. The photocell lassembly is intended for use in an analogue to digital optical encoder in which the regions between electrodes of each group are masked oil from illumination, although it is to be understood that the photocell assembly has applications in addition to that of an optical encoder.
tends between each of the electrodes of the. group 10 remote from the ends of the electrodes confronting'the Also, it is an object of the present invention toy The group lll of electrodes is fabricated as an integral unit due to a bar-shaped portion 18 which exelectrodes of the group 14, thus forming a common connection for the electrodes in group 10.
The base plate 1 2 must be constructed of electrically insulating material and must not be soluble in the electrolyte. Glass has been found to be a preferred material for the base plate 12., although ceramics and plastics may also be employed.
The first step in the fabrication of the photocell assembly is to place a coating of a metal of the platinum group, such as rhodium, designated 2S in FIGURE 3, on one surface of the base plate 12. Since rhodium coating of glass is conventional in the manufacture of mirrors, this step will not be further described.
After the coating has been placed upon a surface of the glass plate 12, a suitable resist 22 in layer form having the pattern of the two groups 1f) and 14 of electrodes is disposed upon the coating 2f). This may be accomplished by painting a resist 22 onto the coating 20 through a stencil; suitable resists for this process being thermoplastic enamels or wax and rosin mixtures. Photographic resists may also be employed. The photographic method of placing the pattem of resist upon the coating is more accurate than the stencil method, and the inventors have found that commercially available photographic resists are particularly satisfactory.
When employing a photographic method of disposing a resist in the pattern of the two groups of electrodes upon the coating 20, optical means are employed to expose the resist with an image of the desired pattern. Thereafter, the photographic resist is developed, usually by placing the base plate 12 and exposed resist 22 in a developer. Suitable developers are available commercially for commercially available photographic resists.
When contact potential is employed to maintain the proper potential difference between the electrolyte and the coating 2Q, a mass or lump 24 of metal which forms a couple with the coating ZG to produce the required potential difference is also placed upon the coating 20. The lump 24 may be placed upon the coating 2t) either before or after the resist 22, but in any event must be at least partially exposed from the resist. FIGURE 3 illustrates in solid lines the lump 24 spaced from the pattern of resist 22, and this is the situation when the resist 22 is placed upon the coating 20 prior to the lump.
When the lump 24 is spaced from the resist pattern, the coating 2th will dissolve when immersed in an electrolyte in the region immediately adjacent to the lump 24, and after continuity of the lump and coating 20 is broken, the reaction will cease. In order to maintain continuity between the lump 24 and the coating 2l) during the etching process, a mass of masking material, designated 26 in FIGURE 3, is disposed between the lump 24- and the resist 22. Wax has been found to be a suitable masking compound for the mass 26. When the base plate 12, coating 2f), resist 22, lump 24 and mass 26 of masking compound are immersed in an electrolyte bath, dissolution of the coating 2t) proceeds from the pattern of resist outwardly until all of the exposed coating is removed. The mass `of masking compound may then be physically scraped from the coating 2f) and the assembly re-immersed in the bath of electrolyte to remove `the strip that has maintained contact with the lump 24. This step is generally unnecessary, since the presence of the lump 24 in electrical contact with one group of electrodes generally facilitates electrical connections.
If the lump 24 is partially covered by the resist 22, as indicated by the dotted lines in FIGURE 3 and designated 2S, the mass of masking material 26 is not necessary. Continuity between the lump and coating 2f) is achieved by the resist itself.
The electrolyte employed must not appreciably attack the resist. Further, the inventors have found that for the dissolution of platinum group metals, the electrolyte must contain a hydrohalic acid, that is, an aqueous 4. solution of HF, HCI, HB1' and Hl. Dilute hydrochloric acid has been found to be a particularly suitable electrolyte.
When dissolving a rhodium coating in a halogen acid electrolyte, the proper potential relation between the rhodium body and the electrolyte is obtained by placing a lead-tin lump, commonly known as solder, on the surface of the rhodium body, or coating 29. Solder with equal parts of lead and tin have been found to be particularly advantageous, although lead alone, iron, and cadmium may also be employed. Solder is considered preferable due to the ease with which it can be attached to the coating, `and to its resistance to attack by the electrolyte. Platinum will also dissolve in halogen acid electrolytes with a lump of lead, lead-tin, iron, or cadmium in contact with the platinum body.
After the etching process is completed, the resist defining the electrodes is removed. If commercially available photographic resists are employed, this may be accomplished by immersion in methyl ethyl ketone. The resist may also be removed by physical methods, such as scraping.
The material employed for the photoconductive ribbon may be any photosensitive material. It has been found that particularly satisfactory photosensitive materials are those of the semiconductor class. Cadmium selenide, cadmium sulfide, lead sulfide, lead selenide, zinc selenide, zinc sulfide, zinc telluride, cadmium telluride, germanium, silicon and lead tellnride have all been found to be suitable.
Solder, in the form generally employed and referred to in this specification, is a mixture of lead and tin. Solder, like other lead and tin alloys, contains a euteetic of lead and tin depending upon the relative proportionsy of the lead and tin in the alloy.
Example I The base 12 is a sheet of plate glass, and it is provided with a rhodium coating 20. The rhodium coating 20 is.
then provided with a layer of commercially available photographic resist, and the pattern of the two groups 10 and 14 of electrodes is then focused upon the photo-V graphic resist to expose it. The photographic resist is then developed in a developer for the photographic resist. A drop of solder 24 is placed upon the rhodium coating 20 spaced from the resist pattern 22. A lump 26 of wax is then placed upon the rhodium coating 20 between the lump of solder 24 and the resistant pattern 22, the wax extending into contact with both the solder and the resist pattern. The solder employed is 50-50 solder, i.e., equal parts of lead and tin. A bath containing a normal solution of hydrochloric acid at room temperature is employed to dissolve the rhodium coating 20, and does not appreciably attack the glass base plate 12 or the resist pattern 22. The resist 22 is Ithen removed by immersion in a bath of methyl ethyl ketone, and the ribbon 16 is formed by evaporating a layer of cadmium and selenium onto the base plate 12 and the two groups 10 and 14 of rhodium electrodes formed by the etching process, and heating for a period of one hour at 400 C.
Example Il A coating of rhodium is placed on a sheet of ceramic. A mass of iron is disposed in contact with the rhodium coating. Following the application of the iron mass, the resist consisting of 50% rosin and 50% wax is applied to the rhodium coating with a stencil and brush in the desired pattern. The resist is positioned on the rhodium coating to partially cover the edge of the iron mass. The ceramic, rhodium coating, resist and iron mass are then immersed in a bath of concentrated hydrouoric acid at room temperature. The ceramic, rhodium coating, resist and iron mass are then immersed for the period suliicient to dissolve the unprotected portion of the rhodium coating, approximately five to ten minutes. A suitable solvent ,5 is then employed to remove the wax and rosin composition from the confronting ends of electrodes of both groups. A ribbon is then 'formed by evaporating a layer of lead and selenium on the plate andelectrodes between and in contact with the confronting ends of the electrodes of the two groups. The base, electrodes and ribbon are then baked at a temperature of 400 C. for a period of one hour.
Example III A platinum coating may be etched and used to form the electrodes of a photocell by substituting platinum for rhodium in either of the foregoing examples.
Also in the `foregoing examples, cadmium, or alloys of lead, cadmium and iron may be substituted for the solder or iron. Best results, however, have been achieved by employing solder consisting of 50% lead and 50% tin. Further, it is not necessary that the lump be bonded to the rhodium or platinum surface, as is the case with soldering. The mass of material may be maintained in contact with the rhodium coated surface in any suitable manner. For example, a clip may be coated with solder and clipped on the base plate either before or during immersion so that it contacts the rhodium surface.
Also, the electrolytes may be replaced in Example I, Example 'Il and Example llll by mixtures of acids as long as one of the acids in the mixture is a halogen acid. `For example, a solution of hydrochloric andi sulfuric acid may be employed, or a solution consisting of 50% aqua regia and 50% HF and HC1. ln like manner, other halogen acids may be substituted for those disclosed in the above examples, for example iodic acid.
FIGURE 4 illustrates the method of etching platinum `group metals in a halogen acid electrolyte with a potential source, `according to the teachings of the present invention. The electric potential source, designated `30, is connected between an electrically conducting electrode 32 and the coating of metal of the platinum group, the negative terminal of the source 30 being connected to the coating 20. Both the electrode 32 and the work piece including the coating Ztl are immersed in a body 34 of electrolyte including a halogen acid which is illustrated disposed within a vessel 36.
The inventors have found that the coating 20 must be maintained at a negative potential relative to the electrolyte. When the coating consists of rhodium and the electrolyte hydrochloric acid, this potential supplied by the source must be between 0.75 volt and 1.00 volt for optimum results.
EXAMPLE IV' The base 12 is a sheet of plate glass, and it is provided with a rhodium coating 20. The rhodium coating 20 is thenV provided with a layer of Kodak Photo Resist, andthe pattern of the two groups 10 and 14 of electrodes is then focused upon a photographic resist to expose it. The photographic resist is then developed in a developer for the photographic resist. A brass electrode is disposed in a bath of 1.0 normal solution of hydrochloric acid at room temperature, and connected to the positive terminal of a potential source. The negative terminal of the potential source is connected to the coating of rhodium by acopper wire, and the coating is immersed in the hydrochloricacid. The potential source is adjusted to make the coating 0.82 volt negative relative to the electrolyte, and the dissolution of the rhodium is permitted to complete. The resist 22, is then removed by immersion in a bath of methyl ethyl ketone, and the ribbon ld is formed by evaporating a layer of cadmium and selenium onto the base plate l2 and the two groups l0 and 14 of rhodium electrodes formed by the etching process, and heating for a period of one hour at 400 C.
Similar processes can be carried out for dissolving and etching platinum and the other elements of the platinum group.
by the foregoing disclosure, but rather only by the ap-v pended claims.
The invention claimed is:
1. The method of etching a pattern in a body of metal in the platinum group comprising the steps of contacting the body with a mass of metal from the group consisting of lead, lead-tin, iron and cadmium, placing a layer of resist in the desired pattern on the body, and
`placing the resist, body, and at least a portion of the metal mass in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte.
2. The method of etching an electrical circuit in a rhodium layer comprising the steps of coating a surface of a base constructed of electrically insulating material with a layer of rhodium, placing a mass of metal of the group consisting of lead, lead-tin, iron and cadmium on a portion of the surface of the rhodium layer, placing a layer of resist on the rhodium layer in the desired pattern, and placing the layer of resist, rhodium layer, and at least a portion of the metal mass in contact with an electrolyte consisting essentially of a hydrohalic acid,
the contact potential of the mass and body making the body electrically negative with respect to the electrolyte.
3. The method of etching an electrical circuit in la layer of rhodium comprising the steps of coating a surface of a glass plate with a layer of rhodium, placing a mass of solder comsisting essentially of a mixture of lead and tin on a portion of the surface ofthe rhodium layer, placing a layer of photographic resist on the rhodium layer, optically exposing a pattern of the desired electrical circuit on the photographic resist, developing the resist, and immersing the glass plate, rhodium layer, at least a portion of the mass of solder, and developed resist in an electrolyte consisting of hydrochloric acid, the contact potential of the mass and rhodium layer making the layer electrically negative with respect to th electrolyte.
4. A method of etching a pattern in a rhodium body comprising the steps of placing a mass of solder consisting essentially of a mixture of lead and tin on a portion of the surface of the rhodium. body, placing a layer of photographic resist on the rhodium body, exposing the desired pattern on the photographic resist, developing the photographic resist, and immersing the body, mass of solder, and developed resist in an electrolyte consisting essentially of hydrohalic acid, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte. v
5. The method of etching an electrical' circuit vin rhodium comprising the steps of placing a mass of 'solder consisting essentially of a mixture -of lead and tin on a portion of the surface of the rhodium body, placing a layer of photographic resist on the rhodium body, exposing the desired pattern on the photographic resist, developing the photographic resist, and immersing theV body,
mass of solder, and developed resist in anelectrolyteconsisting of hydrotiuoric acid, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte.
6. The method of etching an electrical circuit in a layer of rhodium comprising the steps of coating a surface ofra glass plate with a layer of rhodium, placing a mass of solder consisting essentially of a mixture of lead and tin in equal parts on a portion of the surface of the rhodium layer, placing a layer of photographic resist on the rhodium layer, optically exposing a pattern of the desired electrical circuit on the photographic resist, developing the resist, immersing the glass plate, rhodium layer, at least a portion of the mass of solder, and developed resist in an electrolyte consisting of hydrochloric acid, the contact potential of the mass of solder and rhodium layer making the rhodium layer electrically negative with respect to the electrolyte, and then immersing the glass plate, resist and remaining rhodium layer in methyl ethyl ketone to remove the remaining resist.
7. The method of etching a pattern in a rhodium body comprising the steps of placing a mass of solder consisting essentially of a mixture of lead and tin on a portion of the surface of the rhodium body, placing a layer of resist in the desired pattern on the rhodium body, placing the resist, rhodium body, and at least a portion of the mass of solder in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte, and removing the remaining resist.
8. The method of etching an electrical circuit in a layer of rhodium comprising the steps of coating a surface of a glass plate with a la er of rhodium, placing a mass of solder consisting of a mixture of lead and tin in equal parts on a portion of the surface of the rhodium layer, placing a layer of photographic resist on the rhodium layer, optically exposing a pattern of the desired electrical circuit on another region of the photographic resist, developing the resist, placing a mass of wax between the mass of solder and the pattern of resist, and immersing the glass plate, rhodium layer, at least a portion of the mass of solder, and developed resist in an electrolyte consisting of hydrochloric acid, the contact potential of the mass of solder and rhodium layer making the rhodium layer electrically negative with respect to the electrolyte.
9. The method of etching an electrical circuit in a layer of rhodium comprising the steps of coating a surface of a base constructed of electrically insulating material with a layer of rhodium, placing a mass of solder consisting essentially of a mixture of lead and tin on a portion of the surface of the rhodium layer, placing a layer of resist on another portion of the rhodium layer in the desired pattern, placing a mass of masking material between the solder and pattern of resist, and placing the resist, rhodium layer, and at least a portion oi the mass of solder in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass and rhodium layer making the layer electrically negative with respect to the electrolyte.
10. The method of etching an electrical circuit in a layer of rhodium comprising the steps of coating one surface of a glass plate with a layer of rhodium, placing a layer of resist of wax and rosin in a desired pattern on the rhodium layer, placing a mass of solder consisting essentially of a mixture of lead and tin on the rhodium layer spaced from the resist, placing a mass of Wax on the rhodium layer extending between the mass of solder and the resist, immersing the glass plate, rhodium layer, and resist layer in an electrolyte consisting of hydrochloric acid to dissolve the rhodium layer adjacent to the layer of resist, mass of wax, and lump of solder, the contact potential of the mass of solder and layer of rhodium making the layer of rhodium electrically negative with respect to the electrolyte, and removing the exposed portion of the resist layer to expose the confronting rhodium electrodes.
l1. The method of etching an electrical circuit in a layer of rhodium comprising the steps of coating a surface of a base constructed of an electrically insulating material with a layer of rhodium, placing a mass consisting essentially of iron on a portion of the surface of the rhodium layer, placing a layer of resist von rhodium layer in the desited pattern, and placing the resist, rhodium layer, and at least a portion of the iron mass in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass of iron and rhodium layer making the layer electrically negative with respect to the electrolyte.
l2. The method of etching an electrical circuit in a layer of rhodium comprising the steps of coating a surface of a base constructed of an electrically insulating material with a layer of rhodium, placing a mass consisting essentially of cadmium on a portion of the surface of the rhodium layer, placing a layer of resist on the rhodium layer in the desired pattern and placing the resist, rhodium layer, and at least a portion of the cadmium mass in contact with an electrolyte consisting essentially of a hydro halic acid, the contact potential of the mass of cadmium and rhodium layer making the layer electrically negative with respect to the electrolyte.
13. The method of etching an electrical circuit in a layer of rhodium comprising the steps of coating a surface of a base constructed of an electrically insulating material with a layer of rhodium, placing a mass consisting essentially of lead on a portion of the surface of the rhodium layer, placing a layer of resist on the rhodium layer in the desired pattern, and placing the resist, rhodium layer, and at least a portion of the lead mass in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass of lead and layer of rhodium making the layer electrically negative with respect to the electrolyte.
14. The method of etching a pattern in rhodium comprising the steps of placing a mass consisting essentially of iron on a portion of the surface of the rhodium body, placing a layer of resist in the desired pattern on the rhodium body, and placing the resist, rhodium body and at least a portion of the mass of iron in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte.
15. The method of etching a pattern in rhodium comprising the steps of placing a mass consisting essentially of cadmium on a portion ofthe surface of the rhodium body, placing a layer of resist in the desired pattern on the rhodium body, and placing the resist, rhodium body and at least a portion of the mass of cadmium in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte.
16. The method of etching a pattern in rhodium comprising the steps of placing a mass consisting essentially of lead on a portion of the surface of the rhodium body, placing a layer of resist in the desired pattern on the rhodium body, and placing the resist, rhodium body and at least a portion of the mass of lead in contact with an electrolyte consisting essentially of a hydrohalic acid, the contact potential of the mass and the body making the body electrically negative with respect to the electrolyte.
17. The method of dissolving a metal body of the platinum group comprising the steps of placing the metal body of the platinum group in contact with an electrolyte consisting essentially of a hydrohalic acid, and contacting the body with a mass of metals of the group consisting of lead, lead-tin, iron and cadmium, said mass being in contact with the electrolyte, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte.
18. The method of dissolving a body of platinum comprising the steps of placing the platinum body in contact with an electrolyte consisting essentially of a hydrohalic acid, `and contacting the body and electrolyte with a mass consisting essentially of lead, the contact potential of the metal mass and body making the body electrically negative with respect to the electrolyte.
19. The method of dissolving a body of platinum corn- 9 prising the steps of placing the platinum body in contact With an electrolyte consisting essentially of a hydrohalic acid, and contacting the body and electrolyte with a mass consisting essentially of iron, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte.
20. The method of dissolving a body of platinum comprising the steps of placing the platinum body in contact with an electrolyte consisting essentially of a hydrohalic acid, and contacting the body and electrolytewith a mass consisting essentially of cadmium, the contact potential of the mass and body making the body electrically negative with respect tothe electrolyte.
21. The method of dissolving a body of platinum cornprising the steps of placing the platinum body in contact with an electrolyte consisting essentially of a hydrohalic acid, and contacting the body and electrolyterwith a mass 10 consisting essentially of solder with approximately equal parts of lead and tin, the contact potential of the mass and body making the body electrically negative with respect to the electrolyte.
References Cited in the tile of this patent UNITED STATES PATENTS 1,779,457 `Zscliiegne1 Oct. 28, 1930 2,057,272 Schumpelt Oct. 13, 1936 2,370,871 Marks Mar. 6, 1945 2,421,607 Fowler June 3, 1947 2,702,252 Sachof Feb. l5, 1955 2,758,074 Black et al Aug. 7, 1956 OTHER REFERENCES Journal of the Electro Chemical Society, vol. 80, 1941, pp. 489-498.
Claims (1)
1. THE METHOD OF ETCHING A PATTERN IN A BODY OF METAL IN THE PLATINUM GROUP COMPRISING THE STEPS OF CONTACTING THE BODY WITH A MASS OF METAL FROM THE GROUP CONSISTING OF LEAD, LEAD-TIN, IRON AND CADMIUM, PLACING A LAYER OF RESIST IN THE DESIRED PATTERN ON THE BODY, AND PLACING THE RESIST, BODY, AND AT LEAST A PORTION OF THE METAL MASS IN CONTACT WITH AN ELECTROLYTE CONSISTING ESSENTIALLY OF A HYDROHALIC ACID, THE CONTACT POTENTIAL OF THE MASS AND BODY MAKING THE BODY ELECTRICALLY NEGATIVE WITH RESPECT TO THE ELECTROLYTE.
Priority Applications (1)
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US651009A US3013956A (en) | 1957-04-05 | 1957-04-05 | Methods of etching metals in the platinum group and producing printed circuits therefrom |
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US651009A US3013956A (en) | 1957-04-05 | 1957-04-05 | Methods of etching metals in the platinum group and producing printed circuits therefrom |
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US3013956A true US3013956A (en) | 1961-12-19 |
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US651009A Expired - Lifetime US3013956A (en) | 1957-04-05 | 1957-04-05 | Methods of etching metals in the platinum group and producing printed circuits therefrom |
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Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3240684A (en) * | 1962-02-21 | 1966-03-15 | Burroughs Corp | Method of etching rhodium plated metal layers and of making rhodium plated printed circuit boards |
US3271282A (en) * | 1963-06-18 | 1966-09-06 | Photo Engravers Res Inc | Process for etching photoengraving copper |
US3471338A (en) * | 1966-10-31 | 1969-10-07 | Texas Instruments Inc | Method of making a fuel cell electrode |
US3650744A (en) * | 1970-03-02 | 1972-03-21 | Gen Electric | Etching method using photopolymerizable vapors as the photoresist |
US3905883A (en) * | 1973-06-20 | 1975-09-16 | Hitachi Ltd | Electrolytic etching method |
US6162365A (en) * | 1998-03-04 | 2000-12-19 | International Business Machines Corporation | Pd etch mask for copper circuitization |
US20160122554A1 (en) * | 2013-06-11 | 2016-05-05 | Specmat, Inc. | Chemical compositions for semiconductor manufacturing processes and/or methods, apparatus made with same, and semiconductor structures with reduced potential induced degradation |
US10619097B2 (en) | 2014-06-30 | 2020-04-14 | Specmat, Inc. | Low-[HF] room temperature wet chemical growth (RTWCG) chemical formulation |
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US1779457A (en) * | 1927-10-07 | 1930-10-28 | Baker & Co Inc | Electrodeposition of platinum metals |
US2057272A (en) * | 1935-04-20 | 1936-10-13 | Baker & Co Inc | Method of stripping rhodium plating |
US2370871A (en) * | 1942-02-07 | 1945-03-06 | Wallace & Tiernan Inc | Chlorine detection by electrode depolarization |
US2421607A (en) * | 1942-04-03 | 1947-06-03 | Harwood B Fowler | Method of making metallic printing screens |
US2702252A (en) * | 1953-10-02 | 1955-02-15 | Lydia A Suchoff | Method of depositing rhodium metal on printed circuits |
US2758074A (en) * | 1953-08-26 | 1956-08-07 | Rca Corp | Printed circuits |
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Publication number | Priority date | Publication date | Assignee | Title |
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US1779457A (en) * | 1927-10-07 | 1930-10-28 | Baker & Co Inc | Electrodeposition of platinum metals |
US2057272A (en) * | 1935-04-20 | 1936-10-13 | Baker & Co Inc | Method of stripping rhodium plating |
US2370871A (en) * | 1942-02-07 | 1945-03-06 | Wallace & Tiernan Inc | Chlorine detection by electrode depolarization |
US2421607A (en) * | 1942-04-03 | 1947-06-03 | Harwood B Fowler | Method of making metallic printing screens |
US2758074A (en) * | 1953-08-26 | 1956-08-07 | Rca Corp | Printed circuits |
US2702252A (en) * | 1953-10-02 | 1955-02-15 | Lydia A Suchoff | Method of depositing rhodium metal on printed circuits |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3240684A (en) * | 1962-02-21 | 1966-03-15 | Burroughs Corp | Method of etching rhodium plated metal layers and of making rhodium plated printed circuit boards |
US3271282A (en) * | 1963-06-18 | 1966-09-06 | Photo Engravers Res Inc | Process for etching photoengraving copper |
US3471338A (en) * | 1966-10-31 | 1969-10-07 | Texas Instruments Inc | Method of making a fuel cell electrode |
US3650744A (en) * | 1970-03-02 | 1972-03-21 | Gen Electric | Etching method using photopolymerizable vapors as the photoresist |
US3905883A (en) * | 1973-06-20 | 1975-09-16 | Hitachi Ltd | Electrolytic etching method |
US6162365A (en) * | 1998-03-04 | 2000-12-19 | International Business Machines Corporation | Pd etch mask for copper circuitization |
US20160122554A1 (en) * | 2013-06-11 | 2016-05-05 | Specmat, Inc. | Chemical compositions for semiconductor manufacturing processes and/or methods, apparatus made with same, and semiconductor structures with reduced potential induced degradation |
US10619097B2 (en) | 2014-06-30 | 2020-04-14 | Specmat, Inc. | Low-[HF] room temperature wet chemical growth (RTWCG) chemical formulation |
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